From Proteopediaproteopedia link
Complex Structures of CBP Bromodomain with H4 ack20 Peptide
[CBP_HUMAN] Note=Chromosomal aberrations involving CREBBP may be a cause of acute myeloid leukemias. Translocation t(8;16)(p11;p13) with KAT6A; translocation t(11;16)(q23;p13.3) with MLL/HRX; translocation t(10;16)(q22;p13) with KAT6B. KAT6A-CREBBP may induce leukemia by inhibiting RUNX1-mediated transcription. Defects in CREBBP are a cause of Rubinstein-Taybi syndrome type 1 (RSTS1) [MIM:180849]. RSTS1 is an autosomal dominant disorder characterized by craniofacial abnormalities, broad thumbs, broad big toes, mental retardation and a propensity for development of malignancies.   
[CBP_HUMAN] Acetylates histones, giving a specific tag for transcriptional activation. Also acetylates non-histone proteins, like NCOA3 and FOXO1. Binds specifically to phosphorylated CREB and enhances its transcriptional activity toward cAMP-responsive genes. Acts as a coactivator of ALX1 in the presence of EP300.   
Publication Abstract from PubMed
Histone lysine acetylation is central to epigenetic control of gene transcription. Bromodomains of chromosomal proteins function as acetyl-lysine (Kac) binding domains. However, how bromodomains recognize site-specific histones remains unanswered. Here, we report three three-dimensional solution structures of the bromodomains of the human transcriptional coactivators CREB-binding protein (CBP) and p300/CBP-associated factor (PCAF) bound to peptides derived from histone acetylation sites at lysines 36 and 9 in H3, and lysine 20 in H4. From structural and biochemical binding analyses, we determine consensus histone recognition by the bromodomains of PCAF and CBP, which represent two different subgroups of the bromodomain family. Through bromodomain residues in the ZA and BC loops, PCAF prefers acetylation sites with a hydrophobic residue at (Kac+2) position and a positively charged or aromatic residue at (Kac+3), whereas CBP favors bulky hydrophobic residues at (Kac+1) and (Kac+2), a positively charged residue at (Kac-1), and an aromatic residue at (Kac-2).
Structural basis of site-specific histone recognition by the bromodomains of human coactivators PCAF and CBP/p300.,Zeng L, Zhang Q, Gerona-Navarro G, Moshkina N, Zhou MM Structure. 2008 Apr;16(4):643-52. PMID:18400184
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.